1. Field of the Invention
The present invention is directed to a fuel processor, and, more particularly, to a control system for a fuel processor.
2. Description of the Related Art
Fuel cell technology is an alternative energy source for more conventional energy sources employing the combustion of fossil fuels. A fuel cell typically produces electricity, water, and heat from a fuel and oxygen. More particularly, fuel cells provide electricity from chemical oxidation-reduction reactions and possess significant advantages over other forms of power generation in terms of cleanliness and efficiency. Typically, fuel cells employ hydrogen as the fuel and oxygen as the oxidizing agent. The power generation is proportional to the consumption rate of the reactants.
A significant disadvantage which inhibits the wider use of fuel cells is the lack of a widespread hydrogen infrastructure. Hydrogen has a relatively low volumetric energy density and is more difficult to store and transport than the hydrocarbon fuels currently used in most power generation systems. One way to overcome this difficulty is the use of xe2x80x9cfuel processorsxe2x80x9d or xe2x80x9creformersxe2x80x9d to convert the hydrocarbons to a hydrogen rich gas stream which can be used as a feed for fuel cells. Hydrocarbon-based fuels, such as natural gas, LPG, gasoline, and diesel, require conversion for use as fuel for most fuel cells. Current art uses multi-step processes combining an initial conversion process with several clean-up processes. The initial process is most often steam reforming (xe2x80x9cSRxe2x80x9d), autothermal reforming (xe2x80x9cATRxe2x80x9d), catalytic partial oxidation (xe2x80x9cCPOXxe2x80x9d), or non-catalytic partial oxidation (xe2x80x9cPOXxe2x80x9d). The clean-up processes are usually comprised of a combination of desulfurization, high temperature water-gas shift, low temperature water-gas shift, selective CO oxidation, or selective CO methanation. Alternative processes include hydrogen selective membrane reactors and filters.
Thus, many types of fuels can be used, some of them hybrids with fossil fuels, but the ideal fuel is hydrogen. If the fuel is, for instance, hydrogen, then the combustion is very clean and, as a practical matter, only the water is left after the dissipation and/or consumption of the heat and the consumption of the electricity. Most readily available fuels (e.g., natural gas, propane and gasoline) and even the less common ones (e.g., methanol and ethanol) include hydrogen in their molecular structure. Some fuel cell implementations therefore employ a xe2x80x9cfuel processorxe2x80x9d that processes a particular fuel to produce a relatively pure hydrogen stream used to fuel the fuel cell.
The operation of fuel processors and fuel cells, however, is highly complicated. The complexity arises from not only the sophistication of the reforming process and the operation of the fuel cell, but also because the fuel processor and fuel operations are typically highly interrelated. Changes in operating conditions in parameters in one or the other of the fuel processor and fuel cell frequently cascade changes in the other, for good or ill. Sometimes these changes happen relatively rapidly, even for the automated controller such power plants (i.e., the fuel processor and fuel cell) typically use. The complexity and interrelatedness of the operations typically generate a lot of data that the automated controller must deal with quickly. Thus, the organization and efficiency of the data management by the automated controller becomes paramount.
The present invention is directed to resolving, or at least reducing, one or all of the problems mentioned above.
The invention comprises an operational cycle for a fuel processor capable of reforming a fuel, the operational cycle including: an off state; a manager check state entered into from the off state, and in which the operational readiness of the fuel processor is checked; a preheat state entered into from the manager check state, and in which the fuel processor preheats gases, including the fuel, for mixing into a process feed stream; a startup state entered into from the preheat state, and in which the fuel processor begins operating under start-up conditions; a run state entered into from the startup state, and in which the fuel processor reforms the process feed stream into a reformate under steady-state conditions; and a shutdown stale entered into any one of the manager check state, preheat state, startup state, and run state. In other aspects, the operational cycle is employed in a fuel processor for a fuel cell and a fuel cell power plant.